Nasolacrimal drainage system implants for drug therapy

ABSTRACT

An implant for insertion through a punctum and into a canalicular lumen of a patient. The implant includes a matrix of material, a therapeutic agent dispersed in the matrix of material, a sheath disposed over a portion of the matrix of material and configured to inhibit the therapeutic agent from being released from the matrix of material into the canalicular lumen and to allow the therapeutic agent to be released from a surface of the matrix of material to a tear film, and a retention structure configured to retain the implant within the canalicular lumen.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation application of U.S. patentapplication Ser. No. 11/695,545, filed Apr. 2, 2007, which claims thebenefit under 35 USC 119(e) of U.S. Provisional Application No.60/787,775 filed on Mar. 31, 2006, and U.S. Provisional Application No.60/871,864, filed on Dec. 26, 2006, the full disclosures of which areincorporated herein by reference.

BACKGROUND OF THE INVENTION

The present application is related to implants for use in or near thenasolacrimal drainage system, with embodiments providing canalicularimplants, lacrimal sac implants, punctal plugs and punctal plugs withdrug delivery capabilities.

A variety of challenges face patients and physicians in the area ofocular drug delivery. In particular, the repetitive nature of thetherapies (multiple injections, instilling multiple eye drop regimensper day), the associated costs, and the lack of patient compliance maysignificantly impact the efficacy of the therapies available, leading toreduction in vision and many times blindness.

Patient compliance in taking the medications, for example instilling theeye drops, can be erratic, and in some cases, patients may not followthe directed treatment regime. Lack of compliance can include, failureto instill the drops, ineffective technique (instilling less thanrequired), excessive use of the drops (leading to systemic sideeffects), and use of non-prescribed drops or failure to follow thetreatment regime requiring multiple types of drops. Many of themedications may require the patient to instill them up to 4 times a day.

In addition to compliance, the cost of at least some eye dropmedications is increasing, leading some patients on limited incomes tobe faced with the choice of buying basic necessities or instead gettingtheir prescriptions filled. Many times insurance does not cover thetotal cost of the prescribed eye drop medication, or in some cases eyedrops containing multiple different medications.

Further, in many cases, topically applied medications have a peak oculareffect within about two hours, after which additional applications ofthe medications should be performed to maintain the therapeutic benefit.In addition, inconsistency in self-administered or ingested medicationregimes can result in a suboptimal therapy. PCT Publication WO 06/014434(Lazar), which is incorporated herein by reference in its entirety, maybe relevant to these and/or other issues associated with eye drops.

One promising approach to ocular drug delivery is to place an implantthat releases a drug in tissue near the eye. Although this approach canoffer some improvement over eye drops, some potential problems of thisapproach may include implantation of the implant at the desire tissuelocation, retention of the implant at the desired tissue location, andsustaining release of the drug at the desired therapeutic level for anextended period of time. For example in the case of glaucoma treatment,undetected and premature loss of an implant can result in no drug beingdelivered, and the patient can potentially suffer a reduction in vision,possibly even blindness.

In light of the above, it would be desirable to provide improved drugdelivery implants that overcome at least some of the above mentionedshortcomings.

BRIEF SUMMARY OF THE INVENTION

The present invention provides improved implant devices, systems andmethods for insertion into a punctum of a patient. In many embodiments,the implant device can be reliably retained in the eye such that thetherapeutic agent can be delivered for an extended period of time.

In a first aspect, embodiments of the present invention provide animplant for insertion into a punctum of a patient. The implant comprisesa drug core having a distal end and a proximal end. The distal end ofthe drug core has a cross section suitable for insertion through apunctum. The drug core comprises a therapeutic agent deliverable intothe eye. A sheath is disposed over a portion of the drug core to defineat least one exposed surface of the drug core. The at least one exposedsurface of the drug core can be located near the proximal end to contacta tear or tear film fluid and release the therapeutic agent attherapeutic levels over a sustained period when the implant is implantedfor use.

In many embodiments, a retention structure is attached to the drug coreto retain the drug core near and/or in the punctum. The retentionstructure may be attached to the drug core via the sheath. The retentionstructure can comprise a hydrogel adapted to expand when the retentionstructure is placed in the punctum. The retention structure can comprisean attachment member having an axially oriented surface. Expansion ofthe hydrogel can urge against the axially oriented surface to retain thehydrogel while the hydrogel is hydrated. The attachment member cancomprise at least one of a protrusion, a flange, a rim, or an openingthrough a portion of the retention structure.

In many embodiments, the retention structure comprises a flange near theat least one exposed surface to retain the surface near the punctum. Theretention structure may have a size suitable to fit at least partiallywithin the canalicular lumen. The retention structure can be expandablebetween a small profile configuration suitable for insertion and a largeprofile configuration to anchor the retention structure in the lumen,and the retention structure can be attached near the distal end of thedrug core. In specific embodiments, the retention structure can slidealong the drug core near the proximal end when the retention structureexpands from the small profile configuration to the large profileconfiguration. A length of the retention structure along the drug corecan be shorter in the large profile configuration than the small profileconfiguration.

In some embodiments, the retention structure is resiliently expandable.The small profile may have a cross section of no more than about 0.2 mm,and the large profile may have a cross section of no more than about 2.0mm. The retention structure may comprise a tubular body having armsseparated by slots. An occlusive element can be mounted to andexpandable with the retention structure to inhibit tear flow. Theretention structure can be disposed at least partially over the drugcore. An occlusive element may inhibit tear flow through the lumen, andthe occlusive element may cover at least a portion of the retentionstructure to protect the lumen from the retention structure.

In many embodiments, the sheath body may comprise a layer disposed overthe drug core to inhibit release of the therapeutic agent through thelayer. The drug core can release the therapeutic agent through theexposed surface. The drug core may releases the therapeutic agent attherapeutic levels throughout a time period of at least one week whenthe implant is implanted with the surface exposed to the tear or tearfilm fluid. The drug core can comprise inclusions of the agent and theagent is soluble in the drug core to provide a substantially uniformrelease rate when the drug core is implanted.

In some embodiments, an occlusive element may inhibit tear fluid flowthrough the canalicular lumen. For example, the occlusive element canshaped to block tear flow through the canalicular lumen.

In many embodiments, an implant for insertion into a punctum of apatient is provided. The implant comprises a therapeutic agent, and amaterial to hold the therapeutic agent. A retention structure isdisposed over at least a portion of the material, and the retentionstructure is expandable from the material to retain the material nearthe punctum.

In many embodiments, the material holds the therapeutic agent in atleast one of a reservoir or a matrix. An occlusive element may besupported by the retention structure. The retention structure may beexpandable between a small profile configuration suitable for insertionand a large profile configuration to anchor the retention structure inthe lumen, and the occlusive element may expand with the retentionstructure.

In another aspect, embodiments of the present invention provide a methodof treating an eye with a therapeutic agent. The method comprisesinserting a retention structure and a distal end of a drug core of animplant into a punctum. A therapeutic agent is delivered from the drugcore to the eye. An exposed surface of the drug core is limited near theproximal end of the drug core with a sheath. The exposed surface maycontact the tear or tear film fluid such that the treatment agentmigrates from the exposed surface to the eye over a sustained periodwhile the drug core is retained near the punctum by the retentionstructure.

In many embodiments, a method of treating an eye with a therapeuticagent is provided. The method comprises inserting a retention structureand a distal end of a drug core through a punctum so that the drug coreis retained near the punctum. The drug core comprises a therapeuticagent deliverable to the eye and wherein an exposed surface of the drugcore located near the proximal end of the drug core. The exposed surfacecontacts the tear or tear film fluid and the treatment agent migratesfrom the exposed surface to the eye over a sustained period while thedrug core is retained near the punctum.

In many embodiments, the retention structure expands from a narrowprofile configuration to a wide profile configuration. The retentionstructure hydrates when inserted through the punctum to expand from anarrow profile configuration to a wide profile configuration.

In many embodiments, a method of treating an eye with a therapeuticagent is provided, the method comprises inserting a retention structurethrough a punctum into a canalicular lumen so that a drug core isanchored to the lumen with the retention structure and releaseseffective amounts of a therapeutic agent into a tear or tear film fluidof the eye. The drug core is removed from the retention structure whilethe retention structure remains anchored to the lumen. A replacementdrug core is attached to the retention structure while the retentionstructure remains anchored to the lumen. At least one exposed surface ofthe replacement drug core releases the therapeutic agent at therapeuticlevels over a sustained period.

In many embodiments, a method for treating an eye is provided. Themethod comprises inserting a distal end of an implant into a punctum. Aretention structure of the implant is expanded so as to inhibitexpulsion of the implant. The expansion of the implant helps to occludea flow of tear fluid through the punctum. A therapeutic agent isdelivered from a proximal end of the implant to the tear fluid adjacentthe eye. Delivery of the therapeutic agent is inhibited distally of theproximal end.

In many embodiments, delivery of the therapeutic agent to the tear isinhibited with a sheath having a portion exposed to the tear fluid. Inspecific embodiments, the retention structure may comprise asuperelastic or shape memory alloy. The retention structure comprise ahydrogel and extends distally of the drug core.

In another aspect many embodiments of the present invention provide animplant for treating an eye. The eye has a tear fluid and a punctum. Theimplant comprises a drug core having a proximal end, a distal end, and across section suitable for insertion into the punctum. A sheath isdisposed over the drug core distally of the proximal end. A swellablematerial is disposed distally of the proximal end. The swellablematerial is adapted to swell after insertion into the punctum to retainthe drug core and occlude the tears in fluid communication with the drugcore.

In many embodiments, wings are connected to the sheath near the proximalend of the drug core. The wings can be sized to remain outside thepunctum so as to retain the proximal end of the drug core near thepunctum.

In many embodiments, an implant for treating an eye is provided. The eyehas a tear fluid and a punctum. The implant comprises a drug core havinga proximal end, a distal end, and a cross section suitable for insertioninto the punctum. A sleeve is disposed over the drug core at leastdistally of the proximal end. A swellable material is disposed distallyof the proximal end and at least partially covered by the sleeve. Theswellable material is adapted to swell after insertion into the punctumto retain the drug core and occlude the tears in fluid communicationwith the drug core.

In many embodiments, the sleeve comprises tabs to retain the punctalplug upon expansion of the swellable material.

In many embodiments, a punctal plug for treating an eye is provided. Theeye has a tear fluid and a punctum. The plug comprises a plug body, anda drug core inside the plug body. The drug core comprises a mixture oftherapeutic agent and a matrix. A surface of the core is exposed to thetear fluid to treat the eye.

In specific embodiments, the drug core is capable of resilient expansionto accommodate a needle inserted therein while the plug is inserted intoa punctum of the eye.

In many embodiments, a punctal plug for treating an eye is provided. Theeye has a tear fluid and a punctum. The plug comprises an expandableretention element to expand and engage the punctum when positioned inthe eye. A body is connected to the expandable retention element andcomprises a protrusion for removal of the retention element from thepunctum.

In many embodiments, the expandable retention element comprises aswellable material and the body is adapted to retain the swellablematerial while the body is removed. In specific embodiments, theswellable material may comprise a hydrogel.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1-1 and 1-2 show anatomical tissue structures of the eye suitablefor use with implants, according to embodiments of the presentinvention;

FIG. 1A shows a top cross sectional view of a sustained release implantto treat an optical defect of an eye, according to an embodiment of thepresent invention;

FIG. 1B shows a side cross sectional view of the sustained releaseimplant of FIG. 1A;

FIG. 1C shows a perspective view of a sustained release implant with acoil retention structure, according to an embodiment of the presentinvention;

FIG. 1D shows a perspective view of a sustained release implant with aretention structure comprising struts, according to an embodiment of thepresent invention;

FIG. 1E shows a perspective view of a sustained release implant with acage retention structure, according to an embodiment of the presentinvention;

FIG. 1F shows a perspective view of a sustained release implantcomprising a core and sheath, according to an embodiment of the presentinvention;

FIG. 1G schematically illustrates a sustained release implant comprisinga flow restricting retention element, a core and a sheath, according toan embodiment of the present invention;

FIG. 2A shows a cross sectional view of a sustained release implant withcore comprising an enlarged exposed surface area, according to anembodiment of the present invention;

FIG. 2B shows a cross sectional view of a sustained release implant witha core comprising an enlarged exposed surface area, according to anembodiment of the present invention;

FIGS. 2C and 2D show perspective view and cross sectional views,respectively, of a sustained release implant with a core comprising areduced exposed surface area, according to an embodiment of the presentinvention;

FIG. 2E shows a cross sectional view of a sustained release implant witha core comprising an enlarged exposed surface area with an indentationand castellation, according to an embodiment of the present invention;

FIG. 2F shows a perspective view of a sustained release implantcomprising a core with folds, according to an embodiment of the presentinvention;

FIG. 2G shows a perspective view of a sustained release implant with acore comprising a channel with an internal porous surface, according toan embodiment of the present invention;

FIG. 2H shows a perspective view of a sustained release implant with acore comprising porous channels to increase drug migration, according toan embodiment of the invention;

FIG. 2I shows a perspective view of a sustained release implant with aconvex exposed drug core surface, according to an embodiment of thepresent invention;

FIG. 2J shows a side view of a sustained release implant with a corecomprising an exposed surface area with several soft brush-like membersextending therefrom, according to an embodiment of the presentinvention;

FIG. 2K shows a side view of a sustained release implant with a drugcore comprising a convex exposed surface and a retention structure,according to an embodiment of the present invention;

FIG. 2L shows a side view of a sustained release implant with a drugcore comprising a concave indented surface to increase exposed surfacearea of the core, according to an embodiment of the present invention;

FIG. 2M shows a side view of a sustained release implant with a drugcore comprising a concave surface with a channel formed therein toincrease an exposed surface area of the core, according to an embodimentof the present invention;

FIG. 3A shows an implant with a sheath body with extensions that attachthe sheath body and core to the retention element, according to anembodiment of the present invention;

FIG. 3B shows an implant with a retention element with an extension thatretains a sheath body and a core, according to an embodiment of thepresent invention;

FIGS. 4A and 4B show a cross-sectional view of an implant with aretention structure that is shorter in length while in a largecross-sectional profile configuration than a small cross-sectionalprofile configuration, according to an embodiment of the presentinvention;

FIG. 5A shows an insertion tool to insert an implant into the punctumwith a plunger that can be depressed, according to an embodiment of thepresent invention;

FIG. 5B shows an insertion tool to insert an implant into the punctumwith a plunger that can slide, according to an embodiment of the presentinvention;

FIG. 6 shows an insertion tool to insert an implant into the punctumwith a sheath that retracts proximally, according to an embodiment ofthe present invention;

FIGS. 7A to 7C schematically illustrate replacement of a drug core and asheath body, according to an embodiment of the present invention;

FIGS. 8A to 8C show deployment of a sustained release implant, accordingto an embodiment of the present invention;

FIG. 9A shows a drug delivery system with a sleeve to hold the drug coreand a hydrogel retention element, according to embodiments of thepresent invention;

FIG. 9B shows a drug delivery system as in FIG. 9A with a hydratedhydrogel retention element, according to embodiments of the presentinvention;

FIG. 9C shows a drug delivery system as in FIG. 9A with a sleevecomprising a silicone collar to rest on the exterior of the punctum,according to embodiments of the present invention;

FIG. 9D shows sleeve a drug delivery system with a taper on the distalcanalicular end of the sleeve to assist with insertion into the punctumand flanges to rest on the exterior of the punctum, according toembodiments of the present invention;

FIG. 9E shows a sleeve of a drug delivery system with a restriction onthe distal canalicular end of the sleeve to retain the hydrogelretention element in the sleeve, according to embodiments of the presentinvention;

FIG. 9F shows the drug delivery system with a hydrogel retention elementduring insertion into the canalicular lumen, according to embodiments ofthe present invention;

FIG. 9G shows a drug delivery system as in FIG. 9F with an expandedhydrogel retention element following insertion into the canalicularlumen, according to embodiments of the present invention;

FIG. 10A shows a drug core insert for use with a punctal plug, accordingto embodiments of the present invention;

FIG. 10B shows a punctal plug comprising an internal cavity with acylindrical shape, according to embodiments of the present invention;

FIG. 10C shows a punctal plug as in FIG. 10B with a drug core as in FIG.10A inserted therein, according to embodiments of the present invention;

FIG. 11 shows a punctal plug drug delivery system comprising a drugcore, and a retention structure that includes a sleeve with wings formedthereon, according to embodiments of the present invention;

FIG. 12A shows a retention structure comprising a sleeve with tabs andhydrogel, according to embodiments of the present invention;

FIG. 12B shows a retention structure as in FIG. 12A with the tabs urgedradially outward in response to hydration of the hydrogel material,according to embodiments of the present invention;

FIG. 12C shows a retention structure comprising a sleeve with tabs andan annular hydrogel expansion member, according to embodiments of thepresent invention;

FIG. 12D shows a retention structure as in 12C comprising a sleeve withtabs and an annular hydrogel expansion member, according to embodimentsof the present invention;

FIG. 13 shows drug delivery device with a hydrogel retention structurecomprising a sleeve with cross holes and lock tabs and/or flanges tohold the hydrogel in place upon expansion of the hydrogel, according toembodiments of the present invention;

FIG. 14A shows a punctal plug with a drug core and retention fins,according to embodiments of the present invention; and

FIG. 14B shows a punctal plug as in 14A the retention fins folded backto retain the plug while the plug is inserted in the canalicular lumen.

DETAILED DESCRIPTION OF THE INVENTION

FIGS. 1-1 and 1-2 show anatomical tissue structures of an eye 2 suitablefor treatment with implants, according to an embodiment of the presentinvention. Eye 2 includes a cornea 4 and an iris 6. A sclera 8 surroundscornea 4 and iris 6 and appears white. A conjunctival layer 9 issubstantially transparent and disposed over sclera 8. A crystalline lens5 is located within the eye. A retina 7 is located near the back of eye2 and is generally sensitive to light. Retina 7 includes a fovea 7F thatprovides high visual acuity and color vision. Cornea 4 and lens 5refract light to form an image on fovea 7F and retina 7. The opticalpower of cornea 4 and lens 5 contribute to the formation of images onfovea 7F and retina 7. The relative locations of cornea 4, lens 5 andfovea 7F are also important to image quality. For example, if the axiallength of eye 2 from cornea 4 to retina 7F is large, eye 2 can bemyopic. Also, during accommodation, lens 5 moves toward cornea 4 toprovide good near vision of objects proximal to the eye.

The anatomical tissue structures shown in FIG. 1-1 also include thelacrimal system, which includes an upper canaliculus 10 and a lowercanaliculus 12, collectively the canaliculae, and the naso-lacrimal ductor sac 14. The upper and lower canaliculae terminate in an upper punctum11 and a lower punctum 13, also referred to as punctal apertures. Thepunctal apertures are situated on a slight elevation at the medial endof the lid margin at the junction 15 of the ciliary and lacrimalportions near the medial canthus 17. The punctal apertures are round orslightly ovoid openings surrounded by a connective ring of tissue. Eachof the punctal openings 11, 13 leads into a vertical portion 10 a, 12 aof the respective canaliculus before turning horizontally to join itsother canaliculus at the entrance of a lacrimal sac 14. The canaliculaeare tubular and lined by stratified squamous epithelium surrounded byelastic tissue which permits the canaliculus to be dilated.

FIG. 1A shows a top cross sectional view of a sustained release implant100 to treat an optical defect of an eye, according to embodiments ofthe present invention. Implant 100 includes a drug core 110. Drug core110 is an implantable structure that retains a therapeutic agent. Drugcore 110 comprises a matrix 170 that contains inclusions 160 oftherapeutic agent. Inclusions 160 will often comprise a concentratedform of the therapeutic agent, for example a crystalline form of thetherapeutic agent, and the therapeutic agent may over time dissolve intomatrix 170 of drug core 110. Matrix 170 can comprise a silicone matrixor the like, and the mixture of therapeutic agent within matrix 170 canbe non-homogeneous. In many embodiments, the non-homogenous mixturecomprises a silicone matrix portion that is saturated with thetherapeutic agent and an inclusions portion comprising inclusions of thetherapeutic agent, such that the non-homogenous mixture comprises amultiphase non-homogenous mixture. In some embodiments, inclusions 160comprise droplets of an oil of the therapeutic agent, for exampleLatanoprost oil. In some embodiments, inclusions 160 may compriseparticles of the therapeutic agent, for example solid Bimatoprostparticles in crystalline form. In many embodiments, matrix 170encapsulates inclusions 160, and inclusions 160 may comprisemicroparticles have dimensions from about 1 μm to about 100 μm. Theencapsulated inclusions dissolve into the surrounding solid matrix, forexample silicone, that encapsulates the micro particles such that matrix170 is substantially saturated with the therapeutic agent while thetherapeutic agent is released from the core.

Drug core 110 is surrounded by a sheath body 120. Sheath body 120 is canbe substantially impermeable to the therapeutic agent, so that thetherapeutic agent is often released from an exposed surface on an end ofdrug core 110 that is not covered with sheath body 120. A retentionstructure 130 is connected to drug core 110 and sheath body 120.Retention structure 130 is shaped to retain the implant in a hollowtissue structure, for example, a punctum of a canaliculus as describedabove.

An occlusive element 140 is disposed on and around retention structure130. Occlusive element 140 is impermeable to tear flow and occludes thehollow tissue structure and may also serve to protect tissues of thetissue structure from retention structure 130 by providing a more benigntissue-engaging surface. Sheath body 120 includes a sheath body portion150 that connects to retention structure 130 to retain sheath body 120and drug core 110. Sheath body portion 150 can include a stop to limitmovement of sheath body 120 and drug core 110. In many embodiments,sheath body portion 150 can be formed with a bulbous tip 150B. Bulboustip 150B can comprise a convex rounded external portion that providesatraumatic entry upon 11 introduction into the canaliculus. In manyembodiments, sheath body portion 150B can be integral with occlusiveelement 140.

FIG. 1B shows a side cross sectional view of the sustained releaseimplant of FIG. 1A. Drug core 110 is cylindrical and shown with acircular cross-section. Sheath body 120 comprises an annular portiondisposed on drug core 110. Retention structure 130 comprises severallongitudinal struts 131. Longitudinal struts 131 are connected togethernear the ends of the retention structure. Although longitudinal strutsare shown, circumferential struts can also be used. Occlusive element140 is supported by and disposed over longitudinal struts 131 ofretention structure 130 and may comprise a radially expandable membraneor the like.

FIG. 1C shows a perspective view of a sustained release implant 102 witha coil retention structure 132, according to an embodiment of thepresent invention. Retention structure 132 comprises a coil and retainsa drug core 112. A lumen, for example channel 112C, may extend throughthe drug core 112 to permit tear flow through the lumen for the deliveryof therapeutic agent for nasal and systemic applications of thetherapeutic agent. In addition or in combination with channel 112C,retention structure 132 and core 112 can be sized to permit tear flowaround the drug core and sheath body while the retention element holdstissue of the canaliculus away from the drug core. Drug core 112 may bepartially covered. The sheath body comprises a first component 122A thatcovers a first end of drug cove 112 and a second component 122B thatcovers a second end of the drug core. An occlusive element can be placedover the retention structure and/or the retention structure can be dipcoated as described above.

FIG. 1D shows a perspective view of a sustained release implant 104 witha retention structure 134 comprising struts, according to an embodimentof the present invention. Retention structure 134 comprises longitudinalstruts and retains a drug core 114. Drug core 114 is covered with asheath body 124 over most of drug core 114. The drug core releasestherapeutic agent through an exposed end and sheath body 124 is annularover most of the drug core as described above. An occlusive element canbe placed over the retention structure or the retention structure can bedip coated as described above. A protrusion that can be engaged with aninstrument, for example a hook, a loop, a suture, or ring 124R, canextend from sheath body 124 to permit removal of the drug core andsheath body together so as to facilitate replacement of the sheath bodyand drug core while the retention structure remains implanted in thecanaliculus. In some embodiments, a protrusion that can be engaged withan instrument comprising hook, a loop, a suture or a ring, can extendfrom retention structure 134 to permit removal of the sustained releaseimplant by removing the retention structure with the protrusion, drugcore and sheath body.

FIG. 1E shows a perspective view of a sustained release implant 106 witha cage retention structure 136, according to an embodiment of thepresent invention. Retention structure 136 comprises several connectedstrands of metal and retains a drug core 116. Drug core 116 is coveredwith a sheath body 126 over most of drug core 116. The drug corereleases therapeutic agent through an exposed end and sheath body 126 isannular over most of the drug core as described above. An occlusiveelement can be placed over the retention structure or the retentionstructure can be dip coated as described above.

FIG. 1F shows a perspective view of a sustained release implantcomprising a core and sheath, according to an embodiment of the presentinvention. Drug core 118 is covered with a sheath body 128 over most ofdrug core 118. The drug core releases therapeutic agent through anexposed end and sheath body 128 is annular over most of the drug core asdescribed above. The rate of therapeutic agent release is controlled bythe surface area of the exposed drug core and materials included withindrug core 118. In many embodiments, the rate of elution of thetherapeutic agent is strongly and substantially related to the exposedsurface area of the drug core and weakly dependent on the concentrationof drug disposed in the inclusions in the drug core. For circularexposed surfaces the rate of elution is strongly dependent on thediameter of the exposed surface, for example the diameter of an exposeddrug core surface near an end of a cylindrical drug core. Such animplant can be implanted in ocular tissues, for example belowconjunctival tissue layer 9 of the eye and either above sclera tissuelayer 8, as shown in FIG. 1F, or only partially within the scleraltissue layer so as not to penetrate the scleral tissue. It should benoted that drug core 118 can be used with any of the retentionstructures and occlusive elements as described herein.

In an embodiment, the drug core is implanted between sclera 8 andconjunctiva 9 without sheath body 128. In this embodiment without thesheath body, the physical characteristics of the drug core can beadjusted to compensate for the increased exposed surface of drug core,for example by reducing the concentration of dissolved therapeutic agentin the drug core matrix as described herein.

FIG. 1G schematically illustrates a sustained release implant 180comprising a flow restricting retention structure 186, a core 182 and asheath 184, according to an embodiment of the present invention. Sheathbody 184 can at least partially cover drug core 182. Drug core 182 maycontain particles of the therapeutic agent therein to provide asustained release of the therapeutic agent. Drug core 182 can include anexposed convex surface area 182A. Exposed convex surface area 182A mayprovide an increased surface area to release the therapeutic agent. Anocclusive element 188 can be disposed over retention structure 186 toblock the flow of tear through the canaliculus. In many embodiments,retention structure 186 can be located within occlusive structure 188 toprovide the occlusive element integrated with the retention structure.Flow restricting retention structure 186 and occlusive element 188 canbe sized to block tear flow through the canaliculus.

The cores and sheath bodies described herein can be implanted in avariety of tissues in several ways. Many of the cores and sheathsdescribed herein, in particular the structures described with referenceto FIGS. 2A to 2J can be implanted alone as punctal plugs.Alternatively, many of the cores and sheath bodies described herein cancomprise a drug core, sheath body, and/or the like so as to be implantedwith the retention structures and occlusive elements described herein.

FIG. 2A shows a cross sectional view of a sustained release implant 200with core comprising an enlarged exposed surface area, according to anembodiment of the present invention. A drug core 210 is covered with asheath body 220. Sheath body 220 includes an opening 220A. Opening 220has a diameter that approximates the maximum cross sectional diameter ofdrug core 210. Drug core 210 includes an exposed surface 210E, alsoreferred to as an active surface. Exposed surface 210E includes 3surfaces: an annular surface 210A, a cylindrical surface 210B and an endsurface 210C. Annular surface 210A has an outer diameter thatapproximates the maximum cross sectional diameter of core 210 and aninner diameter that approximates the outer diameter of cylindricalsurface 210B. End surface 210C has a diameter that matches the diameterof cylindrical surface 210B. The surface area of exposed surface 210E isthe sum of the areas of annular surface 210A, cylindrical surface 210Band end surface 210C. The surface area may be increased by the size ofcylindrical surface area 210B that extends longitudinally along an axisof core 210.

FIG. 2B shows a cross sectional view of a sustained release implant 202with a core 212 comprising an enlarged exposed surface area 212A,according to an embodiment of the present invention. A sheath body 222extends over core 212. The treatment agent can be released from the coreas described above. Exposed surface area 212A is approximately conical,can be ellipsoidal or spherical, and extends outward from the sheathbody to increase the exposed surface area of drug core 212.

FIGS. 2C and 2D show perspective and cross sectional views,respectively, of a sustained release implant 204 with a drug core 214comprising a reduced exposed surface area 214A, according to anembodiment of the present invention. Drug core 214 is enclosed within asheath body 224. Sheath body 22 includes an annular end portion 224Athat defines an opening through which drug core 214 extends. Drug core214 includes an exposed surface 214A that releases the therapeuticagent. Exposed surface 214A has a diameter 214D that is less than amaximum dimension, for example a maximum diameter, across drug core 214.

FIG. 2E shows a cross sectional view of a sustained release implant 206with a drug core 216 comprising an enlarged exposed surface area 216Awith castellation extending therefrom, according to an embodiment of thepresent invention. The castellation includes several spaced apartfingers 216F to provide increased surface area of the exposed surface216A. In addition to increased surface area provided by castellation,drug core 216 may also include an indentation 2161. Indentation 2161 mayhave the shape of an inverted cone. Core 216 is covered with a sheathbody 226. Sheath body 226 is open on one end to provide an exposedsurface 216A on drug core 216. Sheath body 226 also includes fingers andhas a castellation pattern that matches core 216.

FIG. 2F shows a perspective view of a sustained release implant 250comprising a core with folds, according to an embodiment of the presentinvention. Implant 250 includes a core 260 and a sheath body 270. Core260 has an exposed surface 260A on the end of the core that permits drugmigration to the surrounding tear or tear film fluid. Core 260 alsoincludes folds 260F. Folds 260F increase the surface area of core thatis exposed to the surrounding fluid tear or tear film fluid. With thisincrease in exposed surface area, folds 260F increase migration of thetherapeutic agent from core 260 into the tear or tear film fluid andtarget treatment area. Folds 260F are formed so that a channel 260C isformed in core 260. Channel 260C connects to the end of the core to anopening in exposed surface 260A and provides for the migration oftreatment agent. Thus, the total exposed surface area of core 260includes exposed surface 260A that is directly exposed to the tear ortear film fluid and the surfaces of folds 260F that are exposed to thetear or tear film fluids via connection of channel 260C with exposedsurface 260A and the tear or tear film fluid.

FIG. 2G shows a perspective view of a sustained release implant with acore comprising a channel with an internal porous surface, according toan embodiment of the present invention. Implant 252 includes a core 262and sheath body 272. Core 262 has an exposed surface 262A on the end ofthe core that permits drug migration to the surrounding tear or tearfilm fluid. Core 262 also includes a channel 262C. Channel 262Cincreases the surface area of the channel with a porous internal surface262P formed on the inside of the channel against the core. Channel 262Cextends to the end of the core near exposed surface 262A of the core.The surface area of core that is exposed to the surrounding tear or tearfilm fluid can include the inside of core 262 that is exposed to channel262C. This increase in exposed surface area can increase migration ofthe therapeutic agent from core 262 into the tear or tear film fluid andtarget treatment area. Thus, the total exposed surface area of core 262can include exposed surface 260A that is directly exposed to the tear ortear film fluid and porous internal surface 262P that is exposed to thetear or tear film fluids via connection of channel 262C with exposedsurface 262A and the tear or tear film fluid.

FIG. 2H shows a perspective view of a sustained release implant 254 witha core 264 comprising channels to increase drug migration, according toan embodiment of the invention. Implant 254 includes core 264 and sheathbody 274. Exposed surface 264A is located on the end of core 264,although the exposed surface can be positioned at other locations.Exposed surface 264A permits drug migration to the surrounding tear ortear film fluid. Core 264 also includes channels 264C. Channels 264Cextend to exposed surface 264. Channels 264C are large enough that tearor tear film fluid can enter the channels and therefore increase thesurface area of core 264 that is in contact with tear or tear filmfluid. The surface area of the core that is exposed to the surroundingfluid tear or tear film fluid includes the inner surfaces 264P of core262 that define channels 264C. With this increase in exposed surfacearea, channels 264C increase migration of the therapeutic agent fromcore 264 into the tear or tear film fluid and target treatment area.Thus, the total exposed surface area of core 264 includes exposedsurface 264A that is directly exposed to the tear or tear film fluid andinternal surface 264P that is exposed to the tear or tear film fluidsvia connection of channels 262C with exposed surface 264A and the tearor tear film fluid.

FIG. 2I shows a perspective view of a sustained release implant 256 witha drug core 266 comprising a convex exposed surface 266A, according toan embodiment of the present invention. Drug core 266 is partiallycovered with a sheath body 276 that extends at least partially over drugcore 266 to define convex exposed surface 266A. Sheath body 276comprises a shaft portion 276S. Convex exposed surface 266A provides anincreased exposed surface area above the sheath body. A cross sectionalarea of convex exposed surface 266A is larger than a cross sectionalarea of shaft portion 276S of sheath body 276. In addition to the largercross sectional area, convex exposed surface 266A has a larger surfacearea due to the convex shape 16 which extends outward from the core.Sheath body 276 comprises several fingers 276F that support drug core266 in the sheath body and provide support to the drug core to hold drugcore 266 in place in sheath body 276. Fingers 276F are spaced apart topermit drug migration from the core to the tear or tear film fluidbetween the fingers. Protrusions 276P extend outward on sheath body 276.Protrusions 276P can be pressed inward to eject drug core 266 fromsheath body 276. Drug core 266 can be replaced with another drug coreafter an appropriate time, for example after drug core 266 has releasedmost of the therapeutic agent.

FIG. 2J shows a side view of a sustained release implant 258 with a core268 comprising an exposed surface area with several soft brush-likemembers 268F, according to an embodiment of the present invention. Drugcore 268 is partially covered with a sheath body 278 that extends atleast partially over drug core 268 to define exposed surface 268A.Sheath body 278 comprises a shaft portion 278S. Soft brush-like members268F extend outward from drug core 268 and provide an increased exposedsurface area to drug core 268. Soft brush-like members 268F are alsosoft and resilient and easily deflected such that these members do notcause irritation to neighboring tissue. Although drug core 268 can bemade of many materials as explained above, silicone is a suitablematerial for the manufacture of drug core 268 comprises soft brush likemembers 268F. Exposed surface 268A of drug core 268 also includes anindentation 2681 such that at least a portion of exposed surface 268A isconcave.

FIG. 2K shows a side view of a sustained release implant 259 with a drugcore 269 comprising a convex exposed surface 269A, according to anembodiment of the present invention. Drug core 269 is partially coveredwith a sheath body 279 that extends at least partially over drug core269 to define convex exposed surface 269A. Sheath body 279 comprises ashaft portion 279S. Convex exposed surface 269 provides an increasedexposed surface area above the sheath body. A cross sectional area ofconvex exposed surface 269A is larger than a cross sectional area ofshaft portion 279S of sheath body 279. In addition to the larger crosssectional area, convex exposed surface 269A has a larger surface areadue to the convex shape that extends outward on the core. A retentionstructure 289 can be attached to sheath body 279. Retention structure289 can comprise any of the retention structures as describe herein, forexample a coil comprising a super elastic shape memory alloy such asNitinol™. Retention structure 289 can be dip coated to make retentionstructure 289 biocompatible.

FIG. 2L shows a side view of a sustained release implant 230 with a drugcore 232 comprising a concave indented surface 232A to increase exposedsurface area of the core, according to an embodiment of the presentinvention. A sheath body 234 extends at least partially over drug core232. Concave indented surface 232A is formed on an exposed end of drugcore 232 to provide an increased exposed surface area of the drug core.

FIG. 2M shows a side view of a sustained release implant 240 with a drugcore 242 comprising a concave surface 242A with a channel 242C formedtherein to increase an exposed surface area of the core, according to anembodiment of the present invention. A sheath body 244 extends at leastpartially over drug core 242. Concave indented surface 242A is formed onan exposed end of drug core 232 to provide an increased exposed surfacearea of the drug core. Channel 242C formed in drug core 242 to providean increased exposed surface area of the drug core. Channel 242C canextend to concave indented surface 242A such that channel 242C andprovide an increase in surface area of the core exposed to the tear ortear film.

FIG. 3A shows an implant 310 comprising a sheath body 320 withextensions 322, according to an embodiment of the present invention.Extensions 322 attach sheath body 320 to the retention element to retainthe core near the punctum. Sheath body 320 extends over core 330 todefine an exposed surface 332 of core 330. Extensions 322 can beresilient and engage the retention element and/or occlusive element toattach the sheath body core to the retention element to retain the corenear the punctum.

FIG. 3B shows an implant 350 comprising a retention element 380 with anextension 382, according to an embodiment of the present invention.Extension 382 retains a sheath body 360 and a core 370. Sheath body 360extends over core 370 to define an exposed surface 372 of core 370.Exposed surface 372 is disposed near the proximal end of core 370.Extension 382 extends downward to retain core 370 and sheath body 370.

FIGS. 4A and 4B show a cross-sectional view of an implant 400 with aretention structure 430 that is shorter in length while in a largecross-sectional profile configuration than a small cross-sectionalprofile configuration, according to an embodiment of the presentinvention. Implant 400 includes a distal end 402 and a proximal end 404.Implant 400 includes a drug core 410 and a sheath body 420. Sheath body420 at least partially covers drug core 410 and defines an exposedsurface 412 of drug core 410. An occlusive element 440 can be attachedto and supported by retention structure 430. Occlusive element 440 canmove with retention structure 430, for example when retention element430 expands from a small profile configuration to a large profileconfiguration. In many embodiments, the retention structure andocclusive element are sized to correspond to a diameter of thecanaliculus, for example to match a diameter of the 18 canaliculus orslightly larger than the canalicular diameter, so as occlude fluid flowthrough the canaliculus and/or anchor in the canaliculus.

As shown in FIG. 4A, retention structure 430 and occlusive element 440are in a small profile configuration. Such a small profile configurationcan occur while the occlusive element and retention structure are placedin a tip of an insertion tool and covered for deployment. Retentionelement 430 and occlusive element 440 extend fully along the length ofsheath body 420 and drug core 410. Retention element 430 is attached tosheath body 420 near distal end 402. In many embodiments, retentionstructure 430 and occlusive element 440 have diameters that are sized tofit inside and slide within the canaliculus while in the small profileconfiguration, and the retention structure and occlusive element can besized to anchor within the canaliculus while in a second large profileconfiguration.

As shown in FIG. 4B, retention structure 430 and occlusive element 440are in a large profile configuration. Such a large profile configurationcan occur when the occlusive element and retention structure are placedin the canaliculus. In the large profile configuration, the length ofocclusive element 440 and retention structure 430 is shorter than in thesmall profile configuration by a distance 450. The proximal end ofretention structure 430 and occlusive element 440 can slide over sheathbody 420 when the sheath body and retention structure assume the largeprofile configuration such that the proximal end of drug core 410 andsheath body 420 extend from the retention structure and occlusiveelement. In some embodiments, the sheath body is shorter than drug core410 by distance 450 so that more of the drug core is exposed while theretention structure and occlusive element are in the large profileconfiguration than is exposed while the retention structure andocclusive element are in the small profile configuration. In suchembodiments, the retention structure and occlusive element retract toexpose the drug core.

FIGS. 5A to 6 show embodiments of tools that can be used to insert manyof the implants as describe herein.

FIG. 5A shows an insertion tool 500 to insert an implant into thepunctum with a plunger 530 that can be depressed, according to anembodiment of the present invention. Insertion tool 500 includes adilator 510 that can be inserted into the punctum to pre-dilate thepunctum prior to insertion of an implant. An implant 520 can bepre-loaded onto tool 500 prior to dilation of the punctum. An internalwire 540 can be connected to implant 520 to retain the implant.Following pre-dilation of the punctum with dilator 510, tool 500 can beused to insert implant 520 into the punctum. While implant 520 ispositioned in the punctum, plunger 530 can be depressed to engage wire540 and release implant 520 from tool 500. In some embodiments, wire 540may comprise a sharpened needle tip that penetrates implant 520. Implant520 may comprise a drug core with a resilient material, for examplesilicone, such that the drug core material contracts when the needle isremoved.

FIG. 5B shows an insertion tool 550 to insert an implant 570 into thepunctum with a plunger that can slide, according to an embodiment of thepresent invention. Insertion tool 550 includes a dilator 560 with aconical section to dilate the punctum. Implant 550 includes a plunger580 that can slide distally to advance implant 570 into the lumen. Ashaft 590 is connected to plunger 580 to advance implant 570 distallywhen plunger 580 is advanced distally. While the punctum is dilated withdilator 560, plunger 580 can be advanced distally to place implant 570in the canalicular lumen near the punctum. In many embodiments, a buttoncan be depressed to advance distally the implant into the lumen, forexample a button connected to shaft 590 with an intermediate mechanism.

FIG. 6 shows an insertion tool 600 to insert an implant into the punctumwith a sheath 610 that retracts to position the implant in thecanalicular lumen, according to an embodiment of the present invention.At least a portion of sheath 610 is shaped to dilate the punctum. Sheath610 is shaped to hold an implant 620 in a small profile configuration.Insertion tool 600 includes an annular structure 615, which can comprisea portion of a body 605 of insertion tool 600. Sheath 610 and annularstructure 615 are shaped to dilate the punctum and often compriseproximally inclined surfaces to dilate the punctum. Implant 620, sheath610 and annular structure 615 can be at least partially inserted intothe punctum to place the implant in the canalicular lumen. Annularstructure 615 is disposed over sheath 610 so that sheath 610 can beretracted and slide under annular structure 615. A stop 625 can beconnected to body 605 to retain implant 620 at the desired depth withinthe canalicular lumen while sheath 610 is retracted proximally to exposeimplant 620.

Once implant 620 has been positioned in the canalicular lumen at thedesired depth in relation to the punctum, sheath 610 is retracted toexpose implant 620 at the desired location in the canalicular lumen. Aplunger 630 can be used to retract sheath 610. A shaft 640 mechanicallycouples sheath 610 to plunger 630. Thus, retraction of plunger 630 inthe proximal direction can retract sheath 610 in the proximal directionto expose implant 620 at the desired location in the canalicular lumen.Implant 620 can be any of the implants as described herein. Often,implant 620 will comprise a resilient member that expands to a largeprofile configuration when sheath 610 is retracted. In many embodiments,insertion tool 600 can include a dilator to dilate the punctum prior toinsertion of the implant, and the dilator can be positioned on an end ofthe insertion tool that opposes the end loaded with the implant, asdescribed herein above.

FIGS. 7A to 7C schematically illustrate replacement of a drug core 710and a sheath body 720, according to an embodiment of the presentinvention. An implant 700 comprises drug core 710, sheath body 720 and aretention structure 730. Implant 700 can include an occlusive elementsupport by and movable with retention structure 730. Often retentionstructure 730 can assume a first small profile configuration prior toimplantation and a second large profile configuration while implanted.Retention structure 730 is shown in the large profile configuration andimplanted in the canalicular lumen. Sheath body 720 includes extension725A and extension 725B to attach the sheath body and drug core toretention structure 730 so that the sheath body and drug core areretained by retention structure 730. Drug core 710 and sheath body 720can be removed together by drawing drug core 710 proximally as shown byarrow 730. Retention structure 730 can remain implanted in thecanalicular tissue after drug core 710 and sheath body 720 have beenremoved as shown in FIG. 7B. A replacement core 760 and replacementsheath body 770 can be inserted together as shown in FIG. 7C. Suchreplacement can be desirable after drug core 710 has released effectiveamounts of therapeutic agent such that the supply of therapeutic agentin the drug core has diminished and the rate of therapeutic agentreleased is near the minimum effective level. Replacement sheath body770 includes extension 775A and extension 775B. Replacement drug core760 and replacement sheath body 770 can be advanced distally as shown byarrow 790 to insert replacement drug core 760 and replacement sheathbody 770 into retention structure 730. Retention structure 730 remainsat substantially the same location while replacement drug core 760 andreplacement sheath body 770 are inserted into resilient member 730.

FIGS. 8A to 8C show deployment of a sustained release implant, accordingto an embodiment of the present invention. As shown in FIG. 8A, adeployment instrument 810 is inserted into a canaliculus 800 through apunctum 800A. A sustained release implant 820 is loaded into a tip ofdeployment instrument 810, and a sheath 812 covers sustained releaseimplant 820. Retention structure 830 assumes a small profileconfiguration while sheath 812 is positioned over retention structure830. As shown in FIG. 8B, outer sheath 812 of deployment instrument 810is withdrawn to expose a retention structure 830 of sustained releaseimplant 820. The exposed portion of retention element 830 assumes alarge profile configuration. As shown in FIG. 8C, deployment instrument810 has been removed and sustained release implant 820 is implanted incanaliculus 800. A drug core 840 is attached retention structure 830 andretained in the canaliculus. An outer body sheath 850 covers at least aportion of drug core 840 and drug core 840 releases a therapeutic agentinto a liquid tear or tear film 860 near punctum 800A of canaliculus800.

FIG. 9A shows a drug delivery system 900 with a sleeve 930 to hold adrug core 920 and a hydrogel retention element 910, according toembodiments of the present invention. In many embodiments, the collarcomprises silicone. The drug core comprises matrix with a therapeuticagent and can have a sheath as described above. Hydrogel retentionelement 910 can be placed inside sleeve 930, and when placed in thepunctum, the hydrogel retention element 910 expands as it absorbs fluid.The retention element can comprise many materials that swell. The sleeveacts holds the drug core insert and the hydrogel rod together andprevents the hydrogel member from becoming dislodged from the assembleddrug delivery system. As the hydrogel expands the silicone collar givesslightly to allow expansion and at the same time forms a tighterrestriction around the hydrogel element so as to prevent movement of thehydrogel out of the sleeve. In FIG. 9A, the drug delivery system isshown with the hydrogel retention element in the pre-insertionconfiguration with a slender profile for insertion through the punctuminto the canaliculus. The hydrogel is not substantially hydrated in thenarrow profile configuration and has a water content of less than about10%, for example 1%.

FIG. 9B shows drug delivery system 900 as in FIG. 9A with hydrogelretention element 910 hydrated, according to embodiments of the presentinvention. In the inserted configuration the hydrogel is hydrated andexpanded in the canaliculus. This expansion can tightly fit many sizesof patients due to the broad range of expansion of the hydrogel. In manyembodiments, the silicone sleeve can take additional forms to help withpositioning in the punctum. In the expanded configuration, the hydrogelcan assume an equilibrium concentration of water, for example from about50% to 95% water.

FIG. 9C shows a drug delivery system 950 as in FIG. 9A with a sleeve 954comprising a silicone collar 952 to rest on the exterior of the punctum,according to embodiments of the present invention. The collar can besized such that the device does not engage too deeply into the punctum.For example, the collar can rest on the exterior of the punctum.

FIG. 9D shows a sleeve 966 of a drug delivery system 960 with a taper962 on the distal canalicular end of the sleeve to assist with insertioninto the punctum and flanges 964 to rest on the exterior of the punctum,according to embodiments of the present invention. The sleeve cancomprise many flanges for example 2 flanges, 4 flanges, 8 flanges or 16flanges that can be sized to rest of the exterior of the punctum.

FIG. 9E shows a sleeve 974 of a drug delivery system 970 with arestriction 972 on the distal canalicular end of the sleeve to retainthe hydrogel retention element in the sleeve, according to embodimentsof the present invention. Restriction 972 comprises a flange to engagethe hydrogel when the hydrogel expands. Restriction 972 can also beformed with tabs spike and other protrusions to engage the hydrogel asthe hydrogel urges radially outward from an axis of the hydrogelretention element.

FIG. 9F shows a drug delivery system 980 with a hydrogel retentionelement 982 during insertion into a canalicular lumen 984, according toembodiments of the present invention. The retention element is insertedthrough a punctal opening 986 in a narrow profile configuration. Theretention element comprises substantially dry hydrogel in the narrowprofile configuration. In many embodiments, drug delivery systemcomprises flanges on an end of the sleeve opposite the retentionelement, as described above, such that the flanges rest on the exteriorof the punctum while the retention element is expanded in thecanalicular lumen.

FIG. 9G shows drug delivery system 980 as in FIG. 9F with hydrogelretention element 982 expanded following insertion into the canalicularlumen, according to embodiments of the present invention. The hydrogelretention element is expanded to engage the sleeve and has caused aslight elastic deformation of the resilient silicone sleeve. Thehydrogel retention element urges outward with sufficient force to causeslight deformation of the wall of the canalicular lumen 984.

In many embodiments, the drug delivery system comprises a modular systemthat includes a drug insert and a commercially available punctum plugthat can accommodate the drug insert. The drug insert can be adapted tobe placed in the bore of the punctum plug, and can be held in place viaan interference fit between the outer diameter of the drug insert andthe inner diameter of the silicone plug bore. The assembled system canbe packaged and sterilized and delivered to the physician in thisconfiguration.

In many embodiments, a punctal plug for treating dry eye comprises aswellable material connected to a sleeve body without a drug core, forexample many of the swellable materials and sleeve bodies described inFIGS. 9A to 9G. In some embodiments, dry eye can be treated with many ofthe punctal plugs as described herein in which the core does not includea therapeutic agent comprised therein. In many embodiments the tube bodyis sized to occlude the punctum to treat dry eye. In some embodiments,the body may be smaller than the punctum such that the swollen hydrogelcan occlude the punctum. The body can comprises a protrusion comprisinga flange, rim, wing or the like that is sized to remain on the exteriorof the punctum while the body is positioned in the punctum so as tofacilitate removal of the plug body and retention structure from thepunctum while the hydrogel retention element is swollen. Work inrelation to the present invention suggests that current punctal plugscomprising hydrogel may be difficult to remove as the hydrogel may tear,and the structures described herein to retain hydrogel with a body canfacilitate removal of the swollen hydrogel retention element.

FIG. 10A shows a drug core insert 1010 for use with a punctal plug,according to embodiments of the present invention. Drug core insert cancomprise a drug sheath 1014 comprising polyimide and/or many of thematerials that are substantially impermeable to the therapeutic agent asdescribed above. The drug core comprise many of the shapes describedabove, for example a cylindrical rod. A cyanoacrylate film can beapplied to one end of the drug core insert. An opposing end of the drugcore insert is exposed to permit diffusion of the therapeutic agent intothe tear of the eye as described above. In a specific embodiment, thedrug core insert comprises a cross sectional size, for example adiameter, of about 0.3 mm. A length of the drug core insert is about 0.9mm.

The drug insert may comprise a thin-walled polyimide tube with a drugcore comprising Latanoprost dispersed in Nusil 6385 (MAF 970), a medicalgrade solid silicone that serves as the matrix for drug delivery. Thedistal end of the drug insert can be sealed with a cured film of solidLoctite 4305 medical grade adhesive. Since the drug insert can be placedwithin the bore of the punctum plug, the Loctite 4305 adhesive may notcome into contact with either tissue or the tear film. The innerdiameter of the drug insert can be 0.32 mm; the length can be 0.95 mm.In three embodiments, the Latanoprost concentration can be testedclinically: Drug core containing 3.5, 7 or 14 μg Latanoprost. In manyembodiments, an overall elution rate can be approximately 100 ng/day,and the drug core can comprise 14 μg of Latanoprost, such that the drugcan be delivered for ˜120 days. The overall weight of the drug core,including Latanoprost, can be approximately 70 μg. The weight of thedrug insert including the polyimide sleeve can be approximately 100 μg.

All materials currently being used in the construction of the druginsert are medical grade materials that have passed a battery ofsafety/toxicity tests. The table below summarizes the biocompatibilitytesting performed by the manufacturers on the drug insert materials.

In many embodiments, the drug core can comprise silicone. Latanoprost,at the desired concentration, can be dispersed in uncured Nusil 6385silicone, injected into a polyimide sleeve, and cured at roomtemperature. This method can result in a solid silicone matrixcomprising the desired concentration of Latanoprost.

In many embodiments, the sleeve can comprise polyimide. The polyimidesleeve can house the drug core so as to provide structural support and abarrier to lateral drug diffusion. The inner diameter of the sleeve canbe 0.32 mm, and the wall thickness can be 0.013 mm.

FIG. 10B shows a punctal plug 1020 comprising an internal cavity 1022with a cylindrical shape, according to embodiments of the presentinvention. Cavity 1022 is sized to 10 receive drug core insert 1010 witha friction fit. Punctal plug 1020 can comprise many commerciallyavailable punctal plugs, for example the Medtronic Tear Pool PunctalPlug, the “Parasol Punctal Occluder System” available from Odyssey ofMemphis, Tenn., and/or the Eagle Vision Plug available from Eagle Visionof Memphis, Tenn. In some embodiments, the punctal plug comprises acustom punctal plug, for example sized custom plugs that are selected inresponse to patient measurements. In many embodiments, the punctal plughas a length of about 2 mm and a width of about 1 mm.

FIG. 10C shows a punctal plug as in FIG. 10B with a drug core as in FIG.10A inserted therein, according to embodiments of the present invention.In many embodiments, insertion and removal of the drug delivery systemcan accomplished in a similar manner as for other commercially availablepunctum plugs. The plug can be inserted into the punctum using forcepsor an insertion tool, for example a tool as shown above with a needlesized for insertion into the core. When placed in the superior (orinferior) punctum of the eye, the proximal end of the drug core isexposed to the tear fluid. As the tears come in contact with the exposedproximal surface of the drug core, the therapeutic agent, for exampleLatanoprost, is slowly eluted. The drug delivery system may be removedusing forceps.

FIG. 11 shows a punctal plug drug delivery system 1100 comprising a drugcore 1140, and a retention structure that includes a sleeve 1110 withwings 1112 formed thereon, according to embodiments of the presentinvention. In many embodiments, the retention structure also comprises ahydrogel retention element 1120. Wings 1112 can limit penetration of thedevice into the punctum such that the wings rest on the exterior of thepunctum while device is retained with hydrogel retention element 1120 inthe canalicular lumen. In many embodiments, wings 1112 prevent theproximal end of the plug from migrating distally into the canalicularlumen. Wings 1112 may aid in removal of the device. A 1150 cap can beincluded near the distal end of the device to limit distal expansion ofthe hydrogel. A suture 1130 can extend from the proximal end to thedistal end to hold the drug core and hydrogel retention element insidesleeve 1110.

FIG. 12A shows a retention structure 1200 comprising a sleeve 1210 withtabs 1212 and hydrogel 1220, according to embodiments of the presentinvention. Retention structure 1200 can be combined with many of thedrug cores described above. Sleeve 1210 comprises an annular shell thatcovers hydrogel 1220. Hydrogel 1220 can have a cylindrical shape to fitinside sleeve 1210. While hydrogel 1220 is dry, retention structure 1200remains in a narrow profile configuration. Tabs 1212 define an openingin sleeve 1210 that permits water to enter hydrogel 1220 when sleeve1210 is inserted into the punctum. In some embodiments, the sleeve mayalso comprise a hydrogel component added to the silicone of the sleeveso that the sleeve also expands to increase retention.

FIG. 12B shows a retention structure 1200 as in FIG. 12A with tabs 1212urged radially outward in response to hydration of the hydrogelmaterial, according to embodiments of the present invention. When waterenters the opening in sleeve 1210, hydrogel 1220 expands to urge tabs1212 radially outward. The retention structure can engage the luminalwall to retain the drug elution device in the canaliculus. As thehydrogel urges outward, the hydrogel expands into the openings near thetabs such that the hydrogel is retained in the sleeve.

FIG. 12C shows a retention structure 1250 comprising a sleeve 1260 withtabs 1262 and an annular hydrogel expansion member 1270, according toembodiments of the present invention. While structure 1250 remains dry,the structure retains a narrow profile configuration. The drug core canbe comprised within the annular sleeve as described above.

FIG. 12D shows a retention structure as in 12C comprising a sleeve withtabs and an annular hydrogel expansion member, according to embodimentsof the present invention. Upon hydration of annular hydrogel expansionmember 1270, the annular hydrogel expansion member urges outward againsttabs 1262 to push the tabs outward against the luminal wall.

FIG. 13 shows a drug delivery device 1300 with a retention structurecomprising a hydrogel retention element 1330, a sleeve 1320 with crossholes 1322 therein and lock tabs 1334 and/or flanges to hold thehydrogel in place upon expansion of the hydrogel, according toembodiments of the present invention. Drug delivery device 1300comprises a drug core insert 1310 as described above. Cross holes 1322permit water to pass and hydrate hydrogel retention element 1330.Expansion of hydrogel retention element 1330 urges some of the hydrogelagainst sleeve 1320 and through cross holes 1322 such that the hydrogelretention element is anchored to sleeve 1320 in response to expansion ofthe hydrogel. Lock tabs 1334 engage hydrogel retention element 1330 asthe retention element expands to anchor hydrogel retention element 1330to sleeve 1320 in response to expansion of the hydrogel retentionelement.

FIG. 14A shows a punctal plug 1400 with a drug core 1410 and retentionfins 1420, according to embodiments of the present invention. Retentionfins 1420 can comprise a resilient material, for example silicone. Drugcore 1410 can comprise many of the drug cores described above and asheath as described above may be positioned over the drug core to definean exposed area as described above.

FIG. 14B shows punctal plug 1400 as in 14A retention fins 1420 foldedback to retain plug 1400 while the plug is inserted in a canalicularlumen 1450. Retention fins 1420 are inclined proximally toward thepunctum. This folding back of fins 1420 can wedge the device in thelumen so as to prevent migration. In some embodiments, the plug cancomprise a sleeve with wings as described above.

Sheath Body

The sheath body comprises appropriate shapes and materials to controlmigration of the therapeutic agent from the drug core. The sheath bodyhouses the core and can fit snugly against the core. The sheath body ismade from a material that is substantially impermeable to thetherapeutic agent so that the rate of migration of the therapeutic agentmay be largely controlled by the exposed surface area of the drug corethat is not covered by the sheath body. In many embodiments, migrationof the therapeutic agent through the sheath body can be about one tenthof the migration of the therapeutic agent through the exposed surface ofthe drug core, or less, often being one hundredth or less. In otherwords, the migration of the therapeutic agent through the sheath body isat least about an order of magnitude less that the migration of thetherapeutic agent through the exposed surface of the drug core. Suitablesheath body materials include polyimide, polyethylene terephthalate”(hereinafter “PET”). The sheath body has a thickness, as defined fromthe sheath surface adjacent the core to the opposing sheath surface awayfrom the core, from about 0.00025″ to about 0.0015″. The total diameterof the sheath that extends across the core ranges from about 0.2 mm toabout 1.2 mm. The core may be formed by dip coating the core in thesheath material. Alternatively or in combination, the sheath body cancomprise a tube and the core introduced into the sheath, for example asa liquid or solid that can be slid, injected and/or extruded into thesheath body tube. The sheath body can also be dip coated around thecore, for example dip coated around a pre-formed core.

The sheath body can be provided with additional features to facilitateclinical use of the implant. For example, the sheath may receive a drugcore that is exchangeable while the retention structure and sheath bodyremain implanted in the patient. The sheath body is often rigidlyattached to the retention structure as described above, and the core isexchangeable while the retention structure retains the sheath body. Inspecific embodiments, the sheath body can be provided with externalprotrusions that apply force to the sheath body when squeezed and ejectthe core from the sheath body. Another drug core can then be positionedin the sheath body. In many embodiments, the sheath body and/orretention structure may have a distinguishing feature, for example adistinguishing color, to show placement such that the placement of thesheath body and/or retention structure in the canaliculus or other bodytissue structure can be readily detected by the patient. The retentionelement and/or sheath body may comprise at least one mark to indicatethe depth of placement in the canaliculus such that the retentionelement and/or sheath body can be positioned to a desired depth in thecanaliculus based on the at least one mark.

Retention Structure

The retention structure comprises an appropriate material that is sizedand shaped so that the implant can be easily positioned in the desiredtissue location, for example the canaliculus. The retention structure ismechanically deployable and typically expands to a desired crosssectional shape, for example with the retention structure comprising asuper elastic shape memory alloy such as Nitinol™. Other materials inaddition to Nitinol™ can be used, for example resilient metals orpolymers, plastically deformable metals or polymers, shape memorypolymers, and the like, to provide the desired expansion. In someembodiments shapeable polymers and coated fibers available fromBiogeneral, Inc. of San Diego, Calif. may be used. Many metals such asstainless steels and non-shape memory alloys can be used and provide thedesired expansion. This expansion capability permits the implant to fitin hollow tissue structures of varying sizes, for example canaliculaeranging from 0.3 mm to 1.2 mm (i.e. one size fits all). Although asingle retention structure can be made to fit canaliculae from 0.3 to1.2 mm across, a plurality of alternatively selectable retentionstructures can be used to fit this range if desired, for example a firstretention structure for canaliculae from 0.3 to about 0.9 mm and asecond retention structure for canaliculae from about 0.9 to 1.2 mm. Theretention structure has a length appropriate to the anatomical structureto which the retention structure attaches, for example a length of about3 mm for a retention structure positioned near the punctum of thecanaliculus. For different anatomical structures, the length can beappropriate to provide adequate retention force, e.g. 1 mm to 15 mmlengths as appropriate.

Although the sheath body and drug core are attached to one end of theretention structure as described above, in many embodiments the otherend of retention structure is not attached to drug core and sheath bodyso that the retention structure can slide over the sheath body and drugcore while the retention structure expands. This sliding capability onone end is desirable as the retention structure may shrink in length asthe retention structure expands in width to assume the desired crosssectional width. However, it should be noted that many embodiments mayemploy a sheath body that does not slide in relative to the core.

In many embodiments, the retention structure can be retrieved fromtissue. A protrusion, for example a hook, a loop, or a ring, can extendfrom the retention structure to facilitate removal of the retentionstructure.

In many embodiments the sheath and retention structure can comprise twoparts.

Occlusive Element

The occlusive element comprises an appropriate material that is sizedand shaped so that the implant can at least partially inhibit, evenblock, the flow of fluid through the hollow tissue structure, forexample lacrimal fluid through the canaliculus. The occlusive materialshown is a thin walled membrane of a biocompatible material, for examplesilicone, that can expand and contract with the retention structure. Theocclusive element is formed as a separate thin tube of material that isslid over the end of the retention structure and anchored to one end ofthe retention structure as described above. Alternatively, the occlusiveelement can be formed by dip coating the retention structure in abiocompatible polymer, for example silicone polymer. The thickness ofthe occlusive element can be in a range from about 0.01 mm to about 0.15mm, and often from about 0.05 mm to 0.1 mm.

Therapeutic Agents

A “therapeutic agent” can comprise a drug may be any of the following ortheir equivalents, derivatives or analogs, including, anti-glaucomamedications, (e.g. adrenergic agonists, adrenergic antagonists (betablockers), carbonic anhydrase inhibitors (CAIs, systemic and topical),parasympathomimetics, prostaglandins and hypotensive lipids, andcombinations thereof), antimicrobial agent (e.g., antibiotic, antiviral,antiparacytic, antifungal, etc.), a corticosteroid or otheranti-inflammatory (e.g., an NSAID), a decongestant (e.g.,vasoconstrictor), an agent that prevents of modifies an allergicresponse (e.g., an antihistamine, cytokine inhibitor, leucotrieneinhibitor, IgE inhibitor, immunomodulator), a mast cell stabilizer,cycloplegic or the like. Examples of conditions that may be treated withthe therapeutic agent(s) include but are not limited to glaucoma, preand post surgical treatments, dry eye and allergies. In someembodiments, the therapeutic agent may be a lubricant or a surfactant,for example a lubricant to treat dry eye.

Exemplary therapeutic agents include, but are not limited to, thrombininhibitors; antithrombogenic agents; thrombolytic agents; fibrinolyticagents; vasospasm inhibitors; vasodilators; antihypertensive agents;antimicrobial agents, such as antibiotics (such as tetracycline,chlortetracycline, bacitracin, neomycin, polymyxin, gramicidin,cephalexin, oxytetracycline, chloramphenicol, rifampicin, ciprofloxacin,tobramycin, gentamycin, erythromycin, penicillin, sulfonamides,sulfadiazine, sulfacetamide, sulfamethizole, sulfisoxazole,nitrofurazone, sodium propionate), antifungals (such as amphotericin Band miconazole), and antivirals (such as idoxuridine trifluorothymidine,acyclovir, gancyclovir, interferon); inhibitors of surface glycoproteinreceptors; antiplatelet agents; antimitotics; microtubule inhibitors;anti-secretory agents; active inhibitors; remodeling inhibitors;antisense nucleotides; anti-metabolites; antiproliferatives (includingantiangiogenesis agents); anticancer chemotherapeutic agents;anti-inflaTnmatories (such as hydrocortisone, hydrocortisone acetate,dexamethasone 21-phosphate, fluocinolone, medrysone, methylprednisolone,prednisolone 21-phosphate, prednisolone acetate, fluoromethalone,betamethasone, triamcinolone, triamcinolone acetonide); non steroidalanti-inflammatories (NSAIDs) (such as salicylate, indomethacin,ibuprofen, diclofenac, flurbiprofen, piroxicam indomethacin, ibuprofen,naxopren, piroxicam and nabumetone). Such anti inflammatory steroidscontemplated for use in the methodology of the present invention,include triamcinolone acetonide (generic name) and corticosteroids thatinclude, for example, triamcinolone, dexamethasone, fluocinolone,cortisone, prednisolone, flumetholone, and derivatives thereof.);antiallergenics (such as sodium chromoglycate, antazoline,methapyriline, chlorpheniramine, cetrizine, pyrilamine,prophenpyridamine); anti proliferative agents (such as 1,3-cis retinoicacid, 5-fluorouracil, taxol, rapamycin, mitomycin C and cisplatin);decongestants (such as phenylephrine, naphazoline, tetrahydrazoline);miotics and anti-cholinesterase (such as pilocarpine, salicylate,carbachol, acetylcholine chloride, physostigmine, eserine, diisopropylfluorophosphate, phospholine iodine, demecarium bromide);antineoplastics (such as carmustine, cisplatin, fluorouracil3;immunological drugs (such as vaccines and immune stimulants); hormonalagents (such as estrogens, -estradiol, progestational, progesterone,insulin, calcitonin, parathyroid hormone, peptide and vasopressinhypothalamus releasing factor); immunosuppressive agents, growth hormoneantagonists, growth factors (such as epidermal growth factor, fibroblastgrowth factor, platelet derived growth factor, transforming growthfactor beta, somatotrapin, fibronectin); inhibitors of angiogenesis(such as angiostatin, anecortave acetate, thrombospondin, anti-VEGFantibody); dopamine agonists; radiotherapeutic agents; peptides;proteins; enzymes; extracellular matrix; components; ACE inhibitors;free radical scavengers; chelators; antioxidants; anti polymerases;photodynamic therapy agents; gene therapy agents; and other therapeuticagents such as prostaglandins, antiprostaglandins, prostaglandinprecursors, including antiglaucoma drugs including beta-blockers such asTimolol, betaxolol, levobunolol, atenolol, and prostaglandin analoguessuch as Bimatoprost, travoprost, Latanoprost etc; carbonic anhydraseinhibitors such as acetazolamide, dorzolamide, brinzolamide,methazolamide, dichlorphenamide, diamox; and neuroprotectants such aslubezole, nimodipine and related compounds; and parasympathomimetricssuch as pilocarpine, carbachol, physostigmine and the like.

The amount of drug associated with the drug-delivery device may varydepending on the particular agent, the desired therapeutic benefit andthe time during which the device is intended to deliver the therapy.Since the devices of the present invention present a variety of shapes,sizes and delivery mechanisms, the amount of drug associated with thedevice will depend on the particular disease or condition to be treated,and the dosage and duration that is desired to achieve the therapeuticeffect. Generally, the amount of drug is at least the amount of drugthat upon release from the device, is effective to achieve the desiredphysiological or pharmacological local or systemic effects.

Embodiments of the drug delivery devices of the present invention can beadapted to provide delivery of drug at a daily rate that issubstantially below the therapeutically effective drop form of treatmentso as to provide a large therapeutic range with a wide safety margin.For example, many embodiments treat the eye with therapeutic levels forextended periods that are no more than 5 or 10 percent of the daily dropdosage. Consequently, during an initial bolus or washout period of aboutone to three days, the implant can elute the therapeutic agent at a ratethat is substantially higher than the sustained release levels and wellbelow the daily drop form dosage. For example, with an average sustainedrelease level of 100 ng per day, and an initial release rate of 1000 to1500 ng per day, the amount of drug initially released is less than the2500 ng of drug that may be present in a drop of drug delivered to theeye. This used use of sustained release levels substantially below theamount of drug in a drop and/or drops administered daily allows thedevice to release a therapeutically beneficial amount of drug to achievethe desired therapeutic benefit with a wide safety margin, whileavoiding an inadequate or excessive amount of drug at the intended siteor region.

An extended period of time may mean a relatively short period of time,for example minutes or hours (such as with the use of an anesthetic),through days or weeks (such as the use of pre-surgical or post-surgicalantibiotics, steroids, or NSAIDs and the like), or longer (such as inthe case of glaucoma treatments), for example months or years (on arecurring basis of use of the device).

For example, a drug such as Timolol maleate, a beta1 and beta2(non-selective) adrenergic receptor blocking agent can be used in thedevice for a release over an extended period of time such as 3 months.Three months is a relatively typical elapsed time between physicianvisits for a glaucoma patient undergoing topical drop therapy with aglaucoma drug, although the device could provide treatment for longer orshorter durations. In the three month example, a 0.25% concentration ofTimolol translates to from 2.5 to 5 mg/1000 μL, typically being 2.5mg/1000 μL. A drop of Timolol for topical application is usually in therange of 40-60 μL, typically being 50 μL. Thus, there may be 0.08-0.15mg, typically being 0.125 mg of Timolol in a drop. There may beapproximately 8% (optionally 6-10%) of the drop left in the eye after 5minutes, so about 10 μg of the drug is available at that time. Timololmay have a bioavailability of 30-50%, which means that from 1.5 to 7.5μg, for example 4 μg of the drug is available to the eye. Timolol isgenerally applied twice a day, so 8 (or 3-15) μg is available to the eyeeach day. Therefore, a delivery device might contain from 270 to 1350μg, for example 720 μg, of the drug for a 90 day, or 3 month, extendedrelease. The drug would be contained within the device and eluted basedon the polymer or drug/hydrogel concentration. The drug can be similarlycontained on the device and eluted for olopatadine hydrochloride(Patanol®) and other drugs in a manner similar to Timolol.

Commercially available solutions of Timolol maleate are available in0.25% and 0.5% preparations, and the initial dosage can be 1 drop twiceper day of 0.25% solution. A 0.25% concentration of Timolol isequivalent to 2.5 mg per 1000 μl. A sustained release quantity ofTimolol released each day from the drug core can be from about 3 to 15ug each day. Although the sustained release quantity delivered each dayfrom the device may vary, a sustained release delivery of about 8 μg perday corresponds to about 3.2% of the 0.250 mg of Timolol applied withtwo drops of a 0.25% solution.

For example, in the case of Latanoprost (Xalatan), a prostaglandin F2αanalogue, this glaucoma medication has concentrations that are about1/10^(th) that of Timolol. Therefore, the amount of drug on theimplantable device, depending on the bioavailability, would besignificantly less—approximately 20-135 μg and typically 50-100 μg—forLatanoprost and other prostaglandin analogues. This also translates to adevice that can either be smaller than one required for a beta blockerdelivery or can house more drug for a longer release period.

A drop of Xalatan contains about 2.5 μg of Latanoprost, assuming a 50 μLdrop volume. Therefore, assuming that about 8% of 2.5 μg is present 5minutes after instillation, only about 200 ng of drug remains on theeye. Based on the Latanoprost clinical trials, this amount is effectivein lowering IOP for at least 24 hours. Pfizer/Pharmacia conductedseveral dose-response studies in support of the NDA for Xalatan. Thedoses ranged from 12.5 μg/mL to 115 μg/mL of Latanoprost. The currentdose of Latanoprost, 50 μg/mL, given once per day, was shown to beoptimal. However, even the lowest doses of 12.5 μg/mL QD or 15 μg/mL BIDconsistently gave about 60-75% of the IOP reduction of the 50 μg/mL QDdose. Based on the assumptions above, a 12.5-μg/mL concentrationprovides 0.625 μg of Latanoprost in a 50 μL drop, which results in onlyabout 50 ng (8%) of drug remaining in the eye after 5 minutes.

In many embodiments, the concentrations of Latanoprost are about1/100^(th), or 1 percent, that of Timolol, and in specific embodimentsthe concentrations of Latanoprost may be about 1/50^(th), or 2 percent,that of Timolol. For example, commercially available solutionpreparations of Latanoprost are available at concentrations 0.005%,often delivered with one drop per day. In many embodiments, thetherapeutically effective concentration of drug released from the deviceper day can be about 1/100th of Timolol, about 30 to 150 ng per day, forexample about 80 ng, assuming tear washout and bioavailability similarto Timolol. For example, the amount of drug on the implantable device,can be significantly less—approximately 1% to 2% of Timolol, for example2.7 to 13.5 μg, and can also be about 3 to 20 μg, for Latanoprost andother prostaglandin analogues. Although the sustained release amount ofLatanoprost released each day can vary, a sustained release of 80 ng perday corresponds to about 3.2% of the 2.5 μg of Latanoprost applied witha single drop of a 0.005% solution

For example, in the case of Bimatoprost (Lumigan), a syntheticprostamide prostaglandin analogue, this glaucoma medication may haveconcentrations that are 1/20^(th) or less than that of Timolol.Therefore, the amount of drug loaded on the extended release device fora 3 to 6 month extended release, depending on the bioavailability, canbe significantly less, approximately 5-30 μg and typically 10-20 μg—forBimatoprost and analogues and derivatives thereof. In many embodiments,the implant can house more drug for a longer sustained release period,for example 20-40 μg for a sustained release period of 6 to 12 monthswith Bimatoprost and its derivatives. This decrease in drugconcentration can also translate to a device that can be smaller thanone required for a beta blocker delivery.

Commercially available solution concentrations of Bimatoprost are 0.03%by weight, often delivered once per day. Although the sustained releaseamount of Bimatoprost released each day can vary, a sustained release of300 μg per day corresponds to about 2% of the μg of Bimatoprost appliedwith a single drop of a 0.03% solution. Work in relation with thepresent invention suggests that even lower sustained release doses ofBimatoprost can provide at least some reduction in intraocular pressure,for example 20 to 200 ng of Bimatoprost and daily sustained releasedosages of 0.2 to 2% of the daily drop dosage.

For example, in the case of Travoprost (Travatan), a prostaglandin F2αanalogue, this glaucoma medication may have concentrations that are 2%or less than that of Timolol. For example, commercially availablesolution concentrations are 0.004%, often delivered once per day. Inmany embodiments, the therapeutically effective concentration of drugreleased from the device per day can be about 65 ng, assuming tearwashout and bioavailability similar to Timolol. Therefore, the amount ofdrug on the implantable device, depending on the bioavailability, wouldbe significantly less. This also translates to a device that can eitherbe smaller than one required for a beta blocker delivery or can housemore drug for a longer release period. For example, the amount of drugon the implantable device, can be significantly less—approximately 1/100of Timolol, for example 2.7 to 13.5 μg, and typically about 3 to 20 μg,for Travoprost, Latanoprost and other prostaglandin F2α analogues.Although the sustained release amount of Latanoprost released each daycan vary, a sustained release of 65 ng per day corresponds to about 3.2%of the 2.0 μg of Travoprost applied with a single drop of a 0.004%solution.

In some embodiments, the therapeutic agent may comprise a corticosteriod, for example fluocinolone acetonide, to treat a target oculartissue. In specific embodiments, fluocinolone acetonide can be releasedfrom the canaliculus and delivered to the retina as a treatment fordiabetic macular edema (DME).

It is also within the scope of this invention to modify or adapt thedevices to deliver a high release rate, a low release rate, a bolusrelease, a burst release, or combinations thereof. A bolus of the drugmay be released by the formation of an erodable polymer cap that isimmediately dissolved in the tear or tear film. As the polymer cap comesin contact with the tear or tear film, the solubility properties of thepolymer enable the cap to erode and the drug is released all at once. Aburst release of a drug can be performed using a polymer that alsoerodes in the tear or tear film based on the polymer solubility. In thisexample, the drug and polymer may be stratified along the length of thedevice so that as the outer polymer layer dissolves, the drug isimmediately released. A high or low release rate of the drug could beaccomplished by changing the solubility of the erodable polymer layer sothat the drug layer released quickly or slowly. Other methods to releasethe drug could be achieved through porous membranes, soluble gels (suchas those in typical ophthalmic solutions), microparticle encapsulationsof the drug, or nanoparticle encapsulation, depending on the size of thedrug molecule.

Drug Core

The drug core comprises the therapeutic agent and materials to providesustained release of the therapeutic agent. The therapeutic agentmigrates from the drug core to the target tissue, for example ciliarymuscles of the eye. The therapeutic agent may optionally be onlyslightly soluble in the matrix so that a small amount of therapeuticagent is dissolved in the matrix and available for release from thesurface of drug core 110. As the therapeutic agent diffuses from theexposed surface of the core to the tear or tear film, the rate ofmigration from the core to the tear or tear film can be related to theconcentration of therapeutic agent dissolved in the matrix. In additionor in combination, the rate of migration of therapeutic agent from thecore to the tear or tear film can be related to properties of the matrixin which the therapeutic agent dissolves. In specific embodiments, therate of migration from the drug core to the tear or tear film can bebased on a silicone formulation. In some embodiments, the concentrationof therapeutic agent dissolved in the drug core may be controlled toprovide the desired rate of release of the therapeutic agent. Thetherapeutic agent included in the core can include liquid, solid, solidgel, solid crystalline, solid amorphous, solid particulate, and/ordissolved forms of the therapeutic agent. In a preferred embodiment, thedrug core comprises a silicone matrix containing the therapeutic agent.The therapeutic agent may comprise liquid or solid inclusions, forexample liquid Latanoprost droplets or solid Bimatoprost particles,respectively, dispersed in the silicone matrix.

The drug core can comprise one or more biocompatible materials capableof providing a sustained release of the therapeutic agent. Although thedrug core is described above with respect to an embodiment comprising amatrix with a substantially non-biodegradable silicone matrix withinclusions of the drug located therein that dissolve, the drug core caninclude structures that provide sustained release of the therapeuticagent, for example a biodegradable matrix, a porous drug core, liquiddrug cores and solid drug cores. A matrix that contains the therapeuticagent can be formed from either biodegradable or non-biodegradablepolymers. A non-biodegradable drug core can include silicone, acrylates,polyethylenes, polyurethane, polyurethane, hydrogel, polyester (e.g.,DACRON® from E. I. Du Pont de Nemours and Company, Wilmington, Del.),polypropylene, polytetrafluoroethylene (PTFE), expanded PTFE (ePTFE),polyether ether ketone (PEEK), nylon, extruded collagen, polymer foam,silicone rubber, polyethylene terephthalate, ultra high molecular weightpolyethylene, polycarbonate urethane, polyurethane, polyimides,stainless steel, nickel-titanium alloy (e.g., Nitinol), titanium,stainless steel, cobalt-chrome alloy (e.g., ELGILOY® from ElginSpecialty Metals, Elgin, Ill.; CONICHROME® from Carpenter Metals Corp.,Wyomissing, Pa.). A biodegradable drug core can comprise one or morebiodegradable polymers, such as protein, hydrogel, polyglycolic acid(PGA), polylactic acid (PLA), poly(L-lactic acid) (PLLA),poly(L-glycolic acid) (PLGA), polyglycolide, poly-L-lactide,poly-D-lactide, poly(amino acids), polydioxanone, polycaprolactone,polygluconate, polylactic acid-polyethylene oxide copolymers, modifiedcellulose, collagen, polyorthoesters, polyhydroxybutyrate,polyanhydride, polyphosphoester, poly(alpha-hydroxy acid) andcombinations thereof. In some embodiments the drug core can comprise atleast one of hydrogel polymer.

Release of Therapeutic Agent at Effective Levels

The rate of release of the therapeutic agent can be related to theconcentration of therapeutic agent dissolved in the drug core. In manyembodiments, the drug core comprises non-therapeutic agents that areselected to provide a desired solubility of the therapeutic agent in thedrug core. The non-therapeutic agent of the drug core can comprisepolymers as described herein and additives. A polymer of the core can beselected to provide the desired solubility of the therapeutic agent inthe matrix. For example, the core can comprise hydrogel that may promotesolubility of hydrophilic treatment agent. In some embodiments,functional groups can be added to the polymer to provide the desiredsolubility of the therapeutic agent in the matrix. For example,functional groups can be attached to silicone polymer.

In some embodiments, additives may be used to control the releasekinetics of therapeutic agent. For example, the additives may be used tocontrol the concentration of therapeutic agent by increasing ordecreasing solubility of the therapeutic agent in the drug core so as tocontrol the release kinetics of the therapeutic agent. The solubilitymay be controlled by providing appropriate molecules and/or substancesthat increase and/or decrease the solubility of the dissolved from ofthe therapeutic agent to the matrix. The solubility of the dissolvedfrom the therapeutic agent may be related to the hydrophobic and/orhydrophilic properties of the matrix and therapeutic agent. For example,surfactants, tinuvin, salts and water can be added to the matrix and mayincrease the solubility of hydrophilic therapeutic agent in the matrix.In addition, oils and hydrophobic molecules and can be added to thematrix and may increase the solubility of hydrophobic treatment agent inthe matrix.

Instead of or in addition to controlling the rate of migration based onthe concentration of therapeutic agent dissolved in the matrix, thesurface area of the drug core can also be controlled to attain thedesired rate of drug migration from the core to the target site. Forexample, a larger exposed surface area of the core will increase therate of migration of the treatment agent from the drug core to thetarget site, and a smaller exposed surface area of the drug core willdecrease the rate of migration of the therapeutic agent from the drugcore to the target site. The exposed surface area of the drug core canbe increased in any number of ways, for example by any of castellationof the exposed surface, a porous surface having exposed channelsconnected with the tear or tear film, indentation of the exposedsurface, protrusion of the exposed surface. The exposed surface can bemade porous by the addition of salts that dissolve and leave a porouscavity once the salt dissolves. Hydrogels may also be used, and canswell in size to provide a larger exposed surface area. Such hydrogelscan also be made porous to further increase the rate of migration of thetherapeutic agent.

Further, an implant may be used that includes the ability to release twoor more drugs in combination, such as the structure disclosed in U.S.Pat. No. 4,281,654 (Shell). For example, in the case of glaucomatreatment, it may be desirable to treat a patient with multipleprostaglandins or a prostaglandin and a cholinergic agent or anadrenergic antagonist (beta blocker), such as Alphagan®, or aprostaglandin and a carbonic anhydrase inhibitor.

In addition, drug impregnated meshes may be used such as those disclosedin US Patent Publication No. 2002/0055701 or layering of biostablepolymers as described in US Patent Publication No. 2005/0129731. Certainpolymer processes may be used to incorporate drug into the devices ofthe present invention such as, so-called “self-delivering drugs” orPolymerDrugs (Polymerix Corporation, Piscataway, N.J.) are designed todegrade only into therapeutically useful compounds and physiologicallyinert linker molecules, further detailed in US Patent Publication No.2005/0048121 (East), hereby incorporated by reference in its entirety.Such delivery polymers may be employed in the devices of the presentinvention to provide a release rate that is equal to the rate of polymererosion and degradation and is constant throughout the course oftherapy. Such delivery polymers may be used as device coatings or in theform of microspheres for a drug depot injectable (such as a reservoir ofthe present invention). A further polymer delivery technology may alsobe adapted to the devices of the present invention such as thatdescribed in US Patent Publication No. 2004/0170685 (Carpenter), andtechnologies available from Medivas (San Diego, Calif.).

In specific embodiments, the drug core matrix comprises a solidmaterial, for example silicone, that encapsulates inclusions of thedrug. The drug comprises molecules which are very insoluble in water andslightly soluble in the encapsulating drug core matrix. The inclusionsencapsulated by the drug core can be micro-particles having dimensionsfrom about 1 μm to about 100 μm across. The drug inclusions can comprisecrystals, for example Bimatoprost crystals, and/or droplets of oil, forexample with Latanoprost oil. The drug inclusions can dissolve into thesolid drug core matrix and substantially saturate the drug core matrixwith the drug, for example dissolution of Latanoprost oil into the soliddrug core matrix. The drug dissolved in the drug core matrix istransported, often by diffusion, from the exposed surface of the drugcore into the tear film. As the drug core is substantially saturatedwith the drug, in many embodiments the rate limiting step of drugdelivery is transport of the drug from the surface of the drug corematrix exposed to the tear film. As the drug core matrix issubstantially saturated with the drug, gradients in drug concentrationwithin the matrix are minimal and do not contribute significantly to therate of drug delivery. As surface area of the drug core exposed to thetear film is nearly constant, the rate of drug transport from the drugcore into the tear film can be substantially constant. Work in relationwith the present invention suggests that the solubility of thetherapeutic agent in water and molecular weight of the drug can effecttransport of the drug from the solid matrix to the tear. In manyembodiments, the therapeutic agent is nearly insoluble in water and hasa solubility in water of about 0.03% to 0.002% by weight and a molecularweight from about 400 grams/mol. to about 1200 grams/mol.

In many embodiments the therapeutic agent has a very low solubility inwater, for example from about 0.03% by weight to about 0.002% by weight,a molecular weight from about 400 grams per mole (g/mol.) to about 1200g/mol, and is readily soluble in an organic solvent. Cyclosporin A (CsA)is a solid with an aqueous solubility of 27.67 μg/mL at 25° C., or about0.0027% by weight, and a molecular weight (M.W.) of 1202.6 g/mol.Latanoprost (Xalatan) is a prostaglandin F2α analogue, a liquid oil atroom temperature, and has an aqueous solubility of 50 μg/mL in water at25° C., or about 0.005% by weight and a M.W. of 432.6 g/mol. Bimatoprost(Lumigan) is a synthetic prostamide analogue, a solid at roomtemperature solubility in water of 300 μg/mL in water at 25° C., or0.03% by weight, and has a M.W. of 415.6 g/mol.

Work in relation with the present invention indicates that naturallyoccurring surfactants in the tear film, for example surfactant D andphospholipids, may effect transport of the drug dissolved in the solidmatrix from the core to the tear film. The drug core can be adapted inresponse to the surfactant in the tear film to provide sustaineddelivery of the drug into the tear film at therapeutic levels. Forexample, empirical data can be generated from a patient population, forexample 10 patients whose tears are collected and analyzed forsurfactant content. Elution profiles in the collected tears for a drugthat is sparingly soluble in water, for example cyclosporine, can alsobe measured and compared with elution profiles in buffer and surfactantsuch that an in vitro model of tear surfactant is developed. An in vitrosolution with surfactant based on this empirical data can be used toadjust the drug core in response to the surfactant of the tear film.

The drug cores may also be modified to utilize carrier vehicles such asnanoparticles or microparticles depending on the size of the molecule tobe delivered such as latent-reactive nanofiber compositions forcomposites and nanotextured surfaces (Innovative Surface Technologies,LLC, St. Paul, Minn.), nanostructured porous silicon, known asBiuSilicon®, including micron sized particles, membranes, woven fiversor micromachined implant devices (pSividia, Limited, UK) and proteinnanocage systems that target selective cells to deliver a drug(Chimeracore).

In many embodiments, the drug insert comprises of a thin-walledpolyimide tube sheath with a drug core comprising Latanoprost dispersedin Nusil 6385 (MAF 970), a medical grade solid silicone that serves asthe matrix for drug delivery. The distal end of the drug insert issealed with a cured film of solid Loctite 4305 medical grade adhesive.The drug insert may be placed within the bore of the punctum plug, theLoctite 4305 adhesive does not come into contact with either tissue orthe tear film. The inner diameter of the drug insert can be 0.32 mm; andthe length can be 0.95 mm. Three Latanoprost concentrations in thefinished drug product can be tested clinically: Drug cores can comprise3.5, 7 or 14 μg Latanoprost, with percent by weight concentrations of 5,10 and 20% respectively. Assuming an overall elution rate ofapproximately 100 ng/day, the drug core comprising 14 μg of Latanoprostis adapted to deliver drug for approximately at least 100 days, forexample 120 days. The overall weight of the drug core, includingLatanoprost, can be ˜70 μg. The weight of the drug insert including thepolyimide sleeve can be approximately 100 μg.

In many embodiments, the drug core may elute with an initial elevatedlevel of therapeutic agent followed by substantially constant elution ofthe therapeutic agent. In many instances, an amount of therapeutic agentreleased daily from the core may be below the therapeutic levels andstill provide a benefit to the patient. An elevated level of elutedtherapeutic agent can result in a residual amount of therapeutic agentand/or residual effect of the therapeutic agent that is combined with asub-therapeutic amount of therapeutic agent to provide relief to thepatient. In embodiments where therapeutic level is about 80 ng per day,the device may deliver about 100 ng per day for an initial deliveryperiod. The extra 20 ng delivered per day can have a beneficial effectwhen therapeutic agent is released at levels below the therapeuticlevel, for example at 60 ng per day. As the amount of drug delivered canbe precisely controlled, an initial elevated dose may not result incomplications and/or adverse events to the patient.

While the exemplary embodiments have been described in some detail, byway of example and for clarity of understanding, those of skill in theart will recognize that a variety of modification, adaptations, andchanges may be employed. Hence, the scope of the present inventionshould be limited solely by the appending claims.

1. An implant for insertion through a punctum and into a canalicularlumen of a patient, the implant comprising: a matrix of material; atherapeutic agent dispersed in the matrix of material; a sheath disposedover a portion of the matrix of material and configured to inhibit thetherapeutic agent from being released from the matrix of material intothe canalicular lumen and to allow the therapeutic agent to be releasedfrom a surface of the matrix of material to a tear film; and a retentionstructure configured to retain the implant within the canalicular lumen.2. The implant according to claim 1, wherein the retention structure isconfigured to engage a luminal wall of the canalicular lumen to retainthe implant within the canalicular lumen.
 3. The implant according toclaim 1, wherein the retention structure is an extension configured towedge the implant in the canalicular lumen to prevent migration of theimplant.
 4. The implant according to claim 1, wherein the retentionstructure comprises a shape memory polymer.
 5. The implant according toclaim 1, wherein the retention structure comprises a fluid swellablematerial.
 6. The implant according to claim 5, wherein the fluidswellable material comprises a hydrogel.
 7. The implant according toclaim 1, wherein the therapeutic agent comprises a prostaglandinanalogue.
 8. The implant according to claim 7, wherein the prostaglandinanalogue is selected from the group consisting of latanoprost,bimatoprost, and travoprost.
 9. The implant according to claim 1,wherein the matrix of material comprises a non-biodegradable polymer.10. The implant according to claim 9, wherein the matrix of materialcomprises silicone or urethane.
 11. An implant for insertion into apunctum of a patient, the implant comprising: a therapeutic agent; abody of material that holds the therapeutic agent; and an expandableretention structure disposed over at least a portion of the body ofmaterial, the expandable retention structure configured to retain thebody of material near the punctum.
 12. The implant according to claim11, wherein the body of material holds the therapeutic agent in areservoir and/or a matrix.
 13. The implant according to claim 12,wherein the body of material is a matrix comprising a non-biodegradablepolymer.
 14. The implant according to claim 13, wherein the matrixcomprises silicone or urethane.
 15. The implant according to claim 11,wherein the therapeutic agent comprises a prostaglandin analogue. 16.The implant according to claim 15, wherein the prostaglandin analogue isselected from the group consisting of latanoprost, bimatoprost, andtravoprost.
 17. The implant according to claim 11, wherein theexpandable retention structure comprises a shape memory polymer.
 18. Theimplant according to claim 11, wherein the expandable retentionstructure comprises a fluid swellable material.
 19. The implantaccording to claim 18, wherein the fluid swellable material comprises ahydrogel.
 20. The implant according to claim 11, wherein the retentionstructure is configured to engage a luminal wall of the canalicularlumen to retain the implant within the canalicular lumen.